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Biomedical subjects

L C Wang

Publications and source records attributed to L C Wang.

At least 91 records · Page 5Linked to original sources
PubMed1996

State-dependent changes of brain endogenous opioids in mammalian hibernation.

Endogenous opioids belonging to three opioid families were measured in different states of the hibernation cycle in brain of the Columbian ground squirrels. Using high-performance liquid chromatography-EC detection, the hypothalamic and septal concentrations of met-enkephalin were found to be significantly higher (p < 0.05) in the hibernating state than that in the nonhibernating state. In contrast, met-enkephalin content in the medulla decreased significantly during hibernation. Leuenkephalin content was only increased in the hypothalamus of hibernating animals. Using radioimmunoassay, dynorphin A-like immunoreactivity was observed to increase in the claustrum and striatum, whereas beta-endorphin-like peptides showed a significant increase in the hypothalamus during hibernation. It is evident that the changes in endogenous opioids in brain during hibernation are state dependent, type specific and region specific. These specific alterations of various endogenous opioids may imply their different roles in hibernation.

Animals↗
PubMed1996

Chemosuppression of retinal axon growth by the mouse optic chiasm.

To determine whether diffusible guidance cues direct retinal axon growth and divergence at the optic chiasm, we cocultured mouse retinal and chiasm explants in collagen gels. The chiasm reduced retinal neurite lengths and numbers, but did not affect commissural or pontine neurite growth. This reduction in growth was equal for all retinal quadrants and occurred without reorienting the direction of neurite extension. The floor plate, another midline guidance locus, also suppressed retinal neurite outgrowth, whereas cortex or cerebellum explants did not. Growth suppression was not mediated by netrin-1, which instead enhanced retinal neurite extension. We propose that chemosuppression may be a general guidance mechanism that acts in intermediate targets to prime growth cones to perceive other, more specific cues.

Animals↗
PubMed1996

No ergogenic effect of ginseng ingestion.

The purpose of this study was to examine the effects of ginseng extract ingestion on physiological responses to intense exercise. Subjects performed a control ride (CN) on a cycle ergometer, followed by placebo (PL) and ginseng (GS) treatments. Ginseng was ingested as 8 or 16 mg/kg body weight daily for 7 days prior to trial GS. Venous blood was sampled for FFA, lactate, and glucose analyses. Due to similar findings for both dose groups, the subjects were considered as one group. Lactate, FFA, VO2, VE, and RPE increased significantly from 10 through 40 min. RER increased during the first 10 min of exercise and then remained stable, with no intertrial differences. Glucose did not vary significantly from 0 to 40 min or among treatments. RPE was significantly greater and time to exhaustion was significantly less during trial CN than PL or GS, while PL and GS trials were similar. The data indicated that with 1 week of pretreatment there is no ergogenic effect of ingesting the ginseng saponin extract.

Adult↗
PubMed1996

Gender influences the magnitude of the inflammatory response within embolic cerebral infarcts in young rats.

BACKGROUND AND PURPOSE: The inflammatory response within cerebral infarcts may have an influence on tissue damage. Since old animals with an impaired immune response have decreased inflammation after experimental cerebral infarction, we postulated that female animals with an increased immune response will have an increased inflammatory response after cerebral infarction. METHODS: Embolic cerebral infarcts were produced by photochemical irradiation of the right carotid artery in 12 female Fischer rats. The inflammatory response within 4-day-old infarcts was quantitated by histology with the use of computer-assisted image analysis and compared with that in 12 male rats from a previous series. RESULTS: Severe infarcts had the most pronounced inflammatory response. Female rats had an increased inflammatory response in infarcts of all severity, which was statistically significant in severe cerebral infarcts even after adjustment for infarct size. Severe infarcts in males were significantly larger than those in females. CONCLUSIONS: Gender influences the outcome of embolic cerebral infarcts after photochemical damage to the carotid artery, both in terms of the magnitude of the inflammatory response and infarct size. There are numerous gender-related differences in neurochemicals, cytokine production, and drug metabolism that may influence tissue damage after stroke and responsiveness to therapeutic intervention. The preponderance of male animals in stroke research may produce results not applicable to female stroke patients. The use of female animals will be required to provide adequate models for the study of stroke in women.

Animals↗
PubMed1996

Retinal axon divergence in the optic chiasm: midline cells are unaffected by the albino mutation.

The visual pathway in albino animals is abnormal in that there is a smaller number of ipsilaterally projecting retinal ganglion cells. There are two possible sites of gene action that could result in such a defect. The first site is the retina where the amount of pigmentation in the retinal pigment epithelium is correlated with the degree of ipsilateral innervation (La Vail et al. (1978) J. Comp. Neurol. 182, 399-422). The second site is the optic chiasm, the site of retinal axon divergence. We investigated these two possibilities through a combination of in vivo and in vitro techniques. Our results demonstrate that the growth patterns of retinal axons and the cellular composition of the optic chiasm in albino mice are similar to those of normally pigmented mice, consistent with the albino mutation exerting its effects in the retina, and not on the cells from the chiasmatic midline. We directly tested whether the albino mutation affects the chiasm by studying 'chimeric' cultures of retinal explants and chiasm cells isolated from pigmented and albino mice. Crossed and uncrossed axons from pigmented or albino retinal explants display the same amount of differential growth when grown on either pigmented or albino chiasm cells, demonstrating that the albino mutation does not disrupt the signals for retinal axon divergence associated with the albino optic chiasm. Furthermore, in vitro, a greater proportion of albino retinal ganglion cells from ventrotemporal retina, origin of uncrossed axons, behave like crossed cells, suggesting that the albino mutation acts by respecifying the numbers of retinal ganglion cells that cross the chiasmatic midline.

Albinism↗
PubMed1995

Modulatory effects of magnolol on potassium-stimulated 5-hydroxytryptamine release from rat cortical and hippocampal slices.

Magnolol, a phenolic constituent of magnolia bark, is a known central nervous system depressant. To examine the possibility that magnolol may elicit its depressant effect by modulating central serotonergic activity, its effect on 35 mM K(+)-stimulated 5-[3H]HT release from rat hippocampal and frontal cortical slices were examined. Inclusion of magnolol (1-100 microM) had no effect on 5-HT release in hippocampal slices but elicited a dose-related inhibition on 5-HT release from cortical slices. The inhibitory effect of magnolol on K(+)-stimulated 5-HT release from the cortex was not affected by either antagonists (metergoline, propranolol, and cyproheptadine) (0.01-10 microM) of various 5-HT receptor subtypes or the voltage-dependent sodium channel blocker tetrodotoxin (1 microM). It is concluded that the suppression of brain 5-HT release by magnolol is site-specific, and the suppression of cortical 5-HT release by magnolol is not via the 5-HT autoreceptors at the 5-HT terminals.

Animals↗
PubMed1995

Thermoregulatory effects of alkaloids isolated from Wu-chu-yu in afebrile and febrile rats.

Dehydroevodiamine (DeHE) and evodiamine (EVO), alkaloids isolated from a Chinese medicinal herb, Wu-chu-yu, exhibit calcium antagonistic activity. Intraperitoneal injections of DeHE (5-20 mg/kg) and EVO (2.5-10 mg/kg) caused a dose-related hypothermia in afebrile rats at an ambient temperature (Ta) of 20 degrees C. Because the heat production of alkaloid-injected rats did not differ from that of the controls, the hypothermic effect likely resulted from increased peripheral heat loss. This suggestion is supported by the finding that both DeHE and EVO did not affect the thermoregulatory response of rats exposed to a Ta of 35 degrees C, at which heat loss was maximized. Injection of the same doses of DeHE and EVO attenuated the febrile response in a dose-related manner, induced by intrahypothalamic injection of exogenous pyrogen. The attenuation of the febrile response was associated with a reduction in heat production. Because DeHE and EVO did not affect HP in afebrile rats at a Ta of either 20 or 35 degrees C, but suppressed the metabolic rate of febrile rats at 20 degrees C, the thermoregulatory effect of DeHE and EVO could involve both a calcium-dependent increase in heat loss and a suppression in heat production; the latter may only be manifested when the set point for thermoregulation is elevated.

Alkaloids↗
PubMed1995

Crossed and uncrossed retinal axons respond differently to cells of the optic chiasm midline in vitro.

In mouse, retinal axon divergence takes place within a cellular specialization localized at the midline of the optic chiasm. To test whether the cells in this locus present cues for differential retinal axon growth, retinal explants were cocultured with cells dissociated from the chiasmatic midline, both taken from day 14-15 embryos, during the principal period of retinal axon divergence. Compared with crossed axons from other retinal regions, axons from ventrotemporal retina, the sole source of uncrossed axons, were shorter, more fasciculated, and fewer in number when growing on chiasm cells. Furthermore, uncrossed axons avoided clusters of chiasm neurons and glia having the composition and arrangement of the midline specialization, but crossed axons readily grew over them. In contrast to the clusters of chiasm cells, however, individual neurons and glia did not elicit differential retinal axon growth. These data demonstrate that cues for divergence derive from cells resident to the chiasm and suggest that cellular interactions among resident midline cells are required to produce these cues.

Animals↗
PubMed1995

Effects of honokiol and magnolol on acetylcholine release from rat hippocampal slices.

To study the possible mechanism through which honokiol and magnolol elicit their central depressant effects, we examined the influence of these two phenolic compounds on 25 mM K(+)-stimulated release of [3H]acetylcholine (ACh) from the rat's hippocampal slices. Honokiol, but not magnolol, elicited a concentration-dependent enhancement of K+-evoked ACh release. Addition of either tetrodotoxin, pilocarpine, or methoctramine had no effect on honokiol-enhanced ACh release. These results suggest that honokiol enhanced K(+)-evoked ACh release directly on hippocampal cholinergic terminals via receptors other than the M2 cholinergic subtypes.

Acetylcholine↗
PubMed1995

Increasing the dietary polyunsaturated fat content alters whole-body utilization of 16:0 and 10:0.

Six healthy adult males were fed four different diets to determine the effects of the quantity of fat (30% or 40% of energy as fat) and type of fat (polyunsaturated or saturated) on utilization of fatty acids. Each diet was fed for 15 d. The ratio of dietary polyunsaturated to saturated fat (P:S) was formulated at either 0.2 or 1.0 at both fat intakes. Subjects provided breath tests to measure background 13C and response to [1-13C]10:0 and [1-13C]16:0 fed with a test meal. Increasing the P:S increased whole-body oxidation of labeled 10:0 by 30% after consumption of both low- and high-fat diets. When labeled 16:0 was fed, the amount of 13C excreted in breath increased by a factor of 2.4 after the low-fat diet with a high P:S compared with the diet with a low P:S. The results suggest that the amount and type of fat in the diet affect utilization of individual fatty acids in normal subjects.

Adult↗
PubMed1995

Optical microscopy. 3. Tracking fluorescently labeled neurons in developing brain.

For decades, time-lapse microscopy has been used to track dynamic events associated with biological phenomena. Time-lapse studies of the developing nervous system have been restricted to analysis of dissociated cell cultures or of a series of static images from living organisms. The advent of new fluorescent dyes and video imaging technology has produced novel views of the behavior of neurons in the context of the developing nervous tissue, such as migrations within and away from proliferative zones and navigation of axonal processes to synaptic targets. After fixation of the tissue preparation, time-lapse monitoring can be followed by other analytical techniques and forms of microscopy, e.g., immunocytochemistry or electron microscopy, producing information on the interactions of individual cells whose behavioral histories are known. The power of video time-lapse microscopy of living brain tissue lies in the firsthand documentation of developmental patterning, which in turn can serve as an experimental assay.

Animals↗
PubMed1995

alpha 2-Macroglobulin gene expression during hibernation in ground squirrels is independent of acute phase response.

alpha 2-Macroglobulin, a major acute phase reactant in many species, increases in the Richardson's ground squirrel (Spermophilus richarsonii) during hibernation at the level of both mRNA and protein. To determine if the pattern of liver gene expression known as the acute phase response is elicited as a normal part of the physiological adaptation of hibernation, acute phase reactants were identified in the Richardson's ground squirrel and were then assayed for changes in mRNA expression in the livers of active and hibernating ground squirrels. Our data demonstrate that alpha 1-antitrypsin, alpha 2-macroglobulin, ceruloplasmin, C-reactive protein, and serum amyloid A are acute phase reactants in the Richardson's ground squirrel. Of these, only alpha 2-macroglobulin (alpha 2M) mRNA increases during hibernation, demonstrating that the entire acute phase response is not elicited as a part of the adaptation for hibernation. Alternatively, data from blood clotting assays of serum from active and hibernating animals support a role for the increase in alpha 2M protein during hibernation in decreasing the coagulative properties of the blood.

Actins↗
PubMed1995

A reproducible model of middle cerebral infarcts, compatible with long-term survival, in aged rats.

BACKGROUND AND PURPOSE: Stroke is a disease associated with aging, but experimental stroke studies are generally done in young male animals. Because there are numerous differences associated with aging, such as an altered immune system and altered neurochemistry, that could affect the outcome of these experiments, a model of reproducible cerebral infarction in aged rats is needed. METHODS: We attempted to produce middle cerebral artery (MCA) infarcts in aged (22 months of age) rats using two standard methods. A nylon suture with a heat-induced bulb was passed through the external carotid artery in seven animals, with an attempt to place the tip at the origin of the MCA. The MCA was ligated through a craniotomy just proximal to the internal cerebral vein in 14 rats. Survival potential was tested by attempting 2-week survival in four rats and 2-month survival in one rat. RESULTS: The suture model failed to produce MCA infarcts, even when the bulb of the suture was properly placed in the MCA. The intracranial MCA occlusion resulted in reproducible MCA infarcts. There were no deaths, including the animals allowed to survive 2 weeks and 2 months. CONCLUSIONS: We conclude that reproducible MCA infarcts can be produced in aged rats by craniotomy and that these lesions may be compatible with long-term survival. This should be a useful technique for studying therapeutic interventions and rehabilitation strategies in an animal model that immunologically and neurochemically more closely resembles humans at risk for stroke.

Aging↗
PubMed1994

Species difference in the modulatory effect of kappa agonist on 5-HT release from ground squirrel and rat hippocampus.

Inclusion of the kappa agonist U50488 in the perifusion medium enhanced K(+)-stimulated 5-HT release from ground squirrel hippocampal slices, but reduced 5-HT outflow in both young and old rats' hippocampal slices. The stimulatory effect of U50488 on 5-HT release from ground squirrel hippocampus was not significantly attenuated by the non-specific opioid antagonist naloxone (10(-5) M), but was completely reversed by the specific kappa antagonist nor-BNI (10(-6)M), and the voltage-dependent sodium channel blocker TTX (10(-6)M). In contrast, the inhibitory effect of U50488 on 5-HT release from the young rat hippocampus was attenuated by naloxone (10(-6)M), but not by nor-BNI (10(-6)M) or TTX (10(-6)M). These results illustrate a significant species difference in the modulatory effect of opioids on neurotransmitter release in the hippocampus.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗